Is occasional internal itching on incision site 19 months post op normal?

The remodeling of the scar may take many months after abdominoplasty. As long as this biologic activity continues the patient may experience itching. Scratching will only aggravate the situation.

It is  normal to experience some itching, specially under incisions because the scarring process last for a long time. Massage it with oil and the fibrosis tissue will be softer and itching better.Dr. Cardenas

Is not normal. It might be a dermatitis or simply dry skin itching.I suggest you to try some moisturizer first before consulting a dermatologist.

This itching may be normal as long as it is not associated with a keloid type scar.  If it is causing your daily distress have your plastic surgeon check it out. 

Maybe injection of long acting local anesthesia, marcaine, would break the itching cycle. Other wise ONLY IN PERSON examination and testing would allow a treatment plan. 

An in person exam is needed for treatment.  The nerves are still growing back, so itching is normal.  Follow up with your Plastic Surgeon to confirm you are healing normally.  Best wishes!